The present invention relates to systems for providing a fluid a seal between a rotating and a stationary portion of a fluid container.
Circular clarifier systems and other large diameter process equipment are important in water treatment, wastewater treatment and mining. In some existing circular clarifier systems, a rotating sludge removal mechanism typically includes a series of pipes which rapidly remove sludge from the bottom of the clarifier. In such sludge removal systems, sludge removal pipes are used to draw the sludge up from the bottom of the clarifier tank and then discharge the sludge to a circular chamber, referred to as a xe2x80x9claunderxe2x80x9d, which typically includes both a rotating portion and a stationary portion. The rotating portion is typically connected to the sludge removal pipes which rotate around the bottom of the clarifier, and the stationary portion is typically connected to a discharge pipe from which the sludge is pumped away from the clarifier for disposal or further processing. Essentially, such a xe2x80x9claunderxe2x80x9d typically resembles an annular shaped fluid drum.
An example of such an existing sludge removal system is seen in U.S. Pat. No. 3,951,819 to Shaffer et al., entitled Sludge Removal System. FIG. 1 is a simplified sectional side elevation view of such a system, and FIG. 2 is a simplified top plan view of such a system. As can be seen in FIGS. 1 and 2, system 10 comprises a launder 12 having an outer rotating portion 12A and a central stationary portion 12B. As can also be seen, water level L1 (outside of launder 12) is higher than water level L2 (inside of launder 12). This differential water level (i.e.: L1-L2) provides the force to cause the sludge to flow from the bottom of the clarifier up through conduits 14, and into launder 12. Specifically, water pressure is created by L1 being higher than L2 such that fluid flows upwardly through conduits 14 (entering at end 13 and exiting into launder 12 through end 15). As such, sludge which has settled to the bottom of clarifier 10 is essentially siphoned from the bottom of the clarifier tank, and is then removed from the clarifier through discharge conduit 18. As portion 12A of the launder rotates in direction R, conduits 14 also rotate in direction R, thereby siphoning sludge from the bottom of the clarifier in a circular fashion. (In a typical clarifier system, a plurality of conduits 14, each having their ends 13 disposed at different radial distances from the center of the clarifier, are used to siphon sludge across the entire bottom surface of the clarifier).
As can be appreciated, a problem with this existing clarifier systems is the problem of providing an effective fluid seal between outer rotating portion 12A and a central stationary portion 12B of launder 12. Specifically, existing clarifier launder seals have tended to suffer from numerous deficiencies, including poor sealing efficiency and rapid wear and tear of the sealing surfaces, due to the fact that center portion 12A of the clarifier launder remains stationary as the outer portion 12B rotates therearound. As it is necessary that water level L2 in launder 12 be kept lower than water level L1 in the rest of clarifier 10, it is necessary to maintain an effective seal between the stationary portion 12B and the rotating portion 12A of launder 12.
FIG. 3 shows a sectional elevation view of a typical existing sealing system 20 adapted for use between rotating portion 12A and stationary portion 12B of launder 12. System 20 comprises a flat horizontal flexible strip 22 which may by annular (or circular) in shape such that it extends across and seals gap 33. Typically flexible strip 22 is made of an elastomer (for example, rubber) which is bent at its outer perimeter by about 90 degrees between inner end 21 and outer perimeter 23. Flexible strip 22 will tend to bounce back or straighten itself such that end 23 pushes against edge 24 of rotating portion 12B of launder 12. As such, flexible strip 22 will thus provide a seal between rotating portion 12B and stationary portion 12A of launder 12. As can be seen, a circular hose 26 can be held in position by a plurality of hose clips 28 to provide further support to flexible strip 22.
Flexible strip 22 deflects to accommodate limited relative lateral motion in direction L between the rotating 12B and fixed 12A portions of launder 12. Unfortunately, the amount of such lateral motion in direction L that can be accommodated is quite limited (typically to fraction of an inch, even for a large diameter seal). Moreover, the rubber portion of the seal (i.e.: flexible strip 22) tends to deteriorate over time and eventually fail. Deterioration of this seal reduces the motive force for sludge withdrawal and dilutes the sludge, reducing the overall clarifier performance.
The present invention provides a fluid seal assembly, which in preferred aspects prevents movement of fluid through an annular gap between an inner edge of a circular hole passing through a first member and a second member having a circular outer perimeter.
As such, the present system is ideally suited for use in wastewater treatment clarifier launders. Specifically, in preferred aspects, the present invention provides a seal which substantially restricts or prevents fluid movement through an annular gap between the rotating and stationary portions of a wastewater clarifier launder. However, the application of the present invention is not so limited. Rather, the present invention can be used to provide a fluid seal across an annular gap between any two members, including any system wherein the first and second members are rotatably positionable with respect to one another.
In various aspects, the present invention can be used to provide a seal across an annular gap between a first and a second member wherein the first member is rotated while the second member remains stationary; or wherein the second member is rotated while the first member remains stationary; or wherein the first and second members are rotated, but at different speeds or in different directions.
In a first aspect of the invention, a first contacting member is positioned to span across the gap, with the first contacting member being attached to either one or the other of the first and second members. A plurality of support assemblies are attached to the same member to which the contacting member is attached. These support assemblies are specifically adapted to bias the first contacting member into contact against the other member to which the contacting member is not attached.
Various modifications are possible. For example, the first contacting member and the various support assemblies may together be attached to the member disposed on either the inner or the outer edges of the gap (i.e.: attached to either the first or second members).
In preferred aspects, the various support assemblies comprise a biasing mechanism, a pivot member and a sealing support assembly. The sealing support assembly pivots about the pivot member with the biasing mechanism urging the sealing support assembly against the first contacting member. This is turn either urges the first contacting member directly against the member to which the first contacting member is not attached, or alternatively, the first contacting member is urged directly against a second contacting member (which is positioned between the first contacting member and the member to which the first contacting member is not attached).
Preferably, the first contacting member, and the optional second contacting member are made of a suitably tough but flexible low friction material, which may optionally include ultra-high molecular weight polyethylene. When a second contacting member is not used, the member to which the first contacting member is not attached (i.e.: the member which the first contacting member is instead biased against) is preferably made of a suitably tough but flexible low friction material, which may optionally include ultra-high molecular weight polyethylene.
Accordingly, in a first aspect of the invention, the first contacting member pushes against, and slides along the surface of, the member to which the first contacting member is not attached. In a second aspect of the invention, the first contacting member pushes against, and slides along the surface of a second contacting member which is attached to the member to which the first contacting member is not attached.